This invention relates to a composite structure adapted to provide thermal insulation for windows.
Window heat loss accounts for about 20-40% of building space heating costs. With continuing increases in fuel costs, existing structures require an inexpensive and practical means for converting single pane glass windows to thermal insulators. Presently employed means include double-pane windows constructed to form a sealed air space between the panes. Alternatively, an equivalent second (storm) window is added to function in conjunction with the window to form an insulating air space. The present insulating means are undesirable since they are expensive to make and to install. Furthermore, even though these double-pane arrangements reduce heat loss due to conduction through the outside glass pane, there is still substantial heat loss caused by convection of the air within the air space which promotes conduction heat loss through the outside pane. Additionally, conventional storm windows reduce cold air infiltration, a major heat loss component, by only 1/3 to 1/2.
It would be desirable to provide a means for thermally insulating glass windows with little or no structural modification. Furthermore, it would be desirable to provide a glass thermal insulation means which requires little or no labor costs and which can be produced without the need for special installation tools. In addition, it would be desirable to provide a thermal insulation means for glass windows which can be modified easily to change its light transmission or reflectance characteristics thereby to permit its preferential use at different exposures of a building. Furthermore, it would be desirable to provide such a thermal insulation means which minimizes convection heat loss and eliminates air infiltration heat loss which can be equal to or greater than the conducted heat loss. It is also desirable to provide a thermal insulation that can be installed independent of weather characteristics and whose installation cost is not dependent on building height (because of the difficulty of access) as is the situation with presently employed means. Additionally, it would be advantageous to provide a window thermal insulation that can be removed and installed, literally in seconds, for cleaning or ventilation purposes and, if provided in two pieces, the lower half of which can be removed and magnetically self-stored over the top half when it is desired to open the window for ventilation or for summer storage. Additionally, it would be advantageous to provide a window thermal insulation that can be removed easily to change the summer/winter solar energy transmission characteristics to maximize total energy savings and/or comfort and to facilitate cleaning or repair of the window insulation or prime window.